Targeting Fibrotic Signaling: A Review of Current Literature and Identification of Future Therapeutic Targets to Improve Wound Healing

Altered actin dynamics is possibly implicated in the inhibition of mechanical stimulation-induced dermal fibroblast differentiation into myofibroblasts

The formation of hypertrophic scars and keloids is strongly associated with mechanical stimulation, and myofibroblasts are known to play a major role in abnormal scar formation. Wounds in patients with neurofibromatosis type 1 (NF1) become inconspicuous and lack the tendency to form abnormal scars. We hypothesized that there would be a unique response to mechanical stimulation and subsequent scar formation in NF1. To test this hypothesis, we investigated the molecular mechanisms of differentiation into myofibroblasts in NF1-derived fibroblasts and neurofibromin-depleted fibroblasts and examined actin dynamics, which is involved in fibroblast differentiation, with a focus on the pathway linking LIMK2/cofilin to actin dynamics. In normal fibroblasts, expression of α-smooth muscle actin (α-SMA), a marker of myofibroblasts, significantly increased after mechanical stimulation, whereas in NF1-derived and neurofibromin-depleted fibroblasts, α-SMA expression did not change. Phosphorylation of cofilin and subsequent actin polymerization did not increase in NF1-derived and neurofibromin-depleted fibroblasts after mechanical stimulation. Finally, in normal fibroblasts treated with Jasplakinolide, an actin stabilizer, α-SMA expression did not change after mechanical stimulation. Therefore, when neurofibromin was dysfunctional or depleted, subsequent actin polymerization did not occur in response to mechanical stimulation, which may have led to the unchanged expression of α-SMA. We believe this molecular pathway can be a potential therapeutic target for the treatment of abnormal scars.

Non-Viral Gene Therapy in Trabecular Meshwork Cells to Prevent Fibrosis in Minimally Invasive Glaucoma Surgery

The primary cause of failure for minimally invasive glaucoma surgery (MIGS) is fibrosis in the trabecular meshwork (TM) that regulates the outflow of aqueous humour, and no anti-fibrotic drug is available for intraocular use in MIGS. The myocardin-related transcription factor/serum response factor (MRTF/SRF) pathway is a promising anti-fibrotic target. This study aims to utilise a novel lipid nanoparticle (LNP) to deliver MRTF-B siRNA into human TM cells and to compare its effects with those observed in human conjunctival fibroblasts (FF). Two LNP formulations were prepared with and without the targeting peptide cΥ, and with an siRNA concentration of 50 nM. We examined the biophysical properties and encapsulation efficiencies of the LNPs, and evaluated the effects of MRTF-B silencing on cell viability, key fibrotic genes expression and cell contractility. Both LNP formulations efficiently silenced MRTF-B gene and were non-cytotoxic in TM and FF cells. The presence of cΥ made the LNPs smaller and more cationic, but had no significant effect on encapsulation efficiency. Both TM and FF cells also showed significantly reduced contractibility after transfection with MRTF-B siRNA LNPs. In TM cells, LNPs with cΥ achieved a greater decrease in contractility compared to LNPs without cΥ. In conclusion, we demonstrate that the novel CL4H6-LNPs are able to safely and effectively deliver MRTF-B siRNA into human TM cells. LNPs can serve as a promising non-viral gene therapy to prevent fibrosis in MIGS.

Influence of Transforming Growth Factors beta 1 and beta 3 in the Scar Formation Process

BACKGROUND

Transforming growth factor-beta (TGF-β) plays an instrumental role in forming scars and keloids. TGF-β isoforms exhibit differential expression, indicating distinct wound healing and scar formation functions. However, the role of TGF-β1 and TGF-β3 in wound healing and scar formation remains unclear. This study aimed to compare the specific roles of TGF-β1 and TGF-β3 in wound healing and scar formation by biomolecular analysis.

MATERIALS AND METHODS

The study was conducted by cell isolation and culture cells from a total of 20 human samples. Normal human fibroblasts (NHF) were isolated from normal human samples and myofibroblasts from the different scar types, namely hypertrophic (HT) and keloid (K) scars. NHF and cells from the HT, and K scar, each of which were divided into 3 sample groups: the untreated control, TGF-β1 (10 µg/mL)-treated group, and TGF-β3 (10 µg/mL)-treated group. The results of confocal microscopy and fluorescence-activated cell sorting experiments were compared.

RESULTS

Both the HT and K groups had higher α-smooth muscle actin (α-SMA) expression than the NHF group in the untreated control group. In comparison with the untreated group, NHFs showed a significant increase in α-SMA expression in the TGF-β1-treated group. HT showed a high α-SMA level, which was statistically significant compared with the normal fibroblasts. In the TGF-β3-treated group, α-SMA expression was slightly increased in NHF as compared with the untreated group. TGF-β3 treated HT exhibited a greater reduction in α-SMA expression than in the TGF-β1 treated HT. K, on the other hand, had only a minimal effect on the treatment of TGF-β1 and TGF-β3.

CONCLUSIONS

The findings suggest that TGF-β3 may play a regulatory role in the wound repair process, which could be useful in the development of scar-reducing therapies for patients with scar-related cosmetic concerns.

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.